Field of the Invention and Related Art Statement
This invention relates to an apparatus for automatic positioning printing films such as color separation films on transparent base films.
In a preparatory step of printing process, a printing film having a picture formed thereon has to be sticked on a transparent base film accurately at a predetermined position thereon.
As illustrated in FIGS. 1A and 1B, a transparent base film 1 has formed therein a plurality of centering holes 1a, 1b and 1c and is placed on a table 2 having centering pins 3a and 3b in such a manner that the pins 3a and 3b are inserted into the holes 1a and 1b, respectively. It should be noted that the table 2 may have an additional centering pin which is to be inserted into the hole 1c of the base film 1. A printing film 4 has a smaller size than the base film 1 and includes four register marks 4a to 4d formed outside a pictorial area 4e. Usually, the register marks 4a to 4d are formed by fine lines each having a width of 0.04 to 0.2 mm. The register marks 4a to 4d on the printing film are formed in such a manner that a horizontal line connecting the horizontally aligned marks 4a and 4b intersects orthogonally with a vertical line connecting the vertically aligned marks 4c and 4d at a center of the pictorial area 4e.
On the surface of table 2 these are formed two mutually orthogonal imaginary lines l.sub.1 and l.sub.2, the line l.sub.1 connecting the centers of centering pins 3a and 3b and the line l.sub.2 being a perpendicular bisector with respect to the line l.sub.1. The printing film 4 has to be positioned on the base film 1 at such a position that the register marks 4a and 4b are coincided with the line l.sub.1 as well as the register marks 4c and 4d are coincided with the line l.sub.2.
In the former known method, after the base film 1 has been placed on the table 2 in position, the printing film 4 is positioned on the base film 1 by inspecting the register marks 4a to 4d on the printing film and the actually described centering lines l.sub.1 and l.sub.2 on the table 2 with the aid of a magnifying lens usually having a magnification of ten.
After the printing film 4 has been positioned on the base film 1 precisely at the given position thereof, the printing film is fixed onto the base film by means of an adhesive tape. In order to obtain clear and sharp multi-color printings, four color separation films have to be placed on respective base films with an accuracy smaller than .+-.20 .mu.m, preferably smaller than .+-.15 .mu.m of repeatability. In practice, it is quite difficult to coincide manually the register marks 4a to 4d with the lines l.sub.1 and l.sub.2 accurately with the aid of the magnifying lens, and this operation requires experienced labor work and a long time period. Further, due to the fatigue of eyes of operator, the precision of the centering might be decreased, so that the quality of printed matters might be deteriorated.